Apparatus, useful for the gravity fed delivery of liquids from one fluid reservoir to another, are known in the art. One example of applications, wherein an apparatus of this type is useful, is in the administration of I.V. solutions to a patient. In this particular use certain features such as maintaining uniform flow over fluctuating fluid reservoir pressures, monitoring the flow rate, and restricting the passage of air through the apparatus to the patient are very important. Additionally, non-vented operation (to eliminate contamination from the air) is desirable.
The prior art devices available for use in this application include the drip chamber described in U.S. Pat. No. 3,664,339. This device includes an upper chamber, a lower chamber and fluid communication means including valve means to provide adjustable fluid flow therebetween. This device is similar to the device of the instant invention in that both have an upper and lower chamber with fluid communication means therebetween however, unlike the instant novel device, the device described in this patent does not provide for uniform flow over varying fluid reservoir pressures. Uniform flow is effected in the instant novel apparatus by including a second fluid communication means between said chambers which allows passage of air but not liquid, thus equalizing the pressure in said chambers. Furthermore, the instant novel apparatus includes a filter valve prior to the exiting of the liquid to the patient. This filter valve is operable when wet to pass liquid but not air therethrough, thus metering the solution and preventing a possible air embolism as well as providing a final filtration of any particulate matter in the liquid.
U.S. Pat. No. 3,521,635 discloses a flow meter de-aerator for use in the administration of parenteral fluids. The apparatus disclosed therein has an upper and lower chamber and a single conduit in communication therebetween. This conduit provides for transfer of either liquid or air between said chambers. When used as an airway the purpose is to force air from the lower chamber into the upper chamber and thereby drive the liquid from said upper chamber into an upwardly extending shaft to dislodge air bubbles from a float device. During use, in the administration of I.V. solution, however, the conduit is filled with said liquid and therefore does not function as an airway. Furthermore, like the device described in U.S. Pat. No. 3,664,339 above, there is no filter provided nor any other valve means prior to the solution exit from the lower chamber. U.S. Pat. Nos. 3,664,339 and 3,776,229 disclose additional examples of other, two chamber, fluid transfer devices having a single conduit therebetween. As with the device described in saids U.S. Pat. No. 3,521,635, obtaining uniform flow over fluctuating fluid reservoir pressures is not possible with devices of this design.
In U.S. Pat. No. 3,929,157, a gravity fed, fluid delivery system is disclosed which includes upper and lower chambers, which are disposed so that the lower chamber receives fluid from said upper chamber via a fluid conduit therebetween; means for maintaining the fluid level in said upper chamber; and vent means which provides communication between said chambers, as well as the outside.
This system, similarly to the system described in U.S. Pat. No. 3,931,818 below, provides a float valve at the liquid exit from the lower chamber. This system, thus suffers the same disadvantages as the system described in that patent.
In U.S. Pat. No. 3,931,818, a non-vented liquid administration system is disclosed which comprises a sump chamber and a float chamber, wherein said chambers are connected by liquid communication means and a pressure equalizing air tube. This device differs from the instant novel device in that float valve means are provided prior to the exit of said liquid from said float chamber. The instant novel apparatus eliminates the possibility of mechanical failure inherent in valves of this type by use of a filter valve which also provides the feature of a final filtration, noted above. Furthermore, float valves require a certain minimum liquid level in said float chamber in order to bouy up the valve member and allow the exiting of liquid. The instant novel apparatus does not require any minimum liquid level in the lower chamber and, in fact, there is no liquid volume maintained above the filter valve in the lower chamber. A device similar to that disclosed in U.S. Pat. No. 3,931,818 is described in U.S. Pat. No. 3,963,024.
In U.S. Pat. Nos. 3,149,758 and 3,631,654, the use of filter valves is described. Nowhere, however, do said patents teach, disclose or suggest the use of said filter valves in the non-vented, gravity fed delivery of liquids from one fluid reservoir to another. These references, however, are hereby incorporated by reference for the purpose of disclosing hydrophobic and hydrophilic filter valves, useful in the apparatus of the instant invention.